A device for monitoring a skin surface for leakage of blood at, for example, a wound or a vascular access. The device comprises a patient unit (12), a connection unit (14) and a monitor unit (16). The patient unit comprises a patch (21), including an adhesive layer (24) to be attached to the skin surface of the patient. The adhesive layer is arranged to attach the patch to the skin so that a predetermined removal force, such as 30N, is required for removing the patch from the skin surface. A patient optical fiber is arranged at the patch and has a proximal end for connection to the connection unit. A patient connector (52) is arranged at the distal end of a connection optical fiber (51). The connector has an opening passing through the connector, whereby the connection optical fiber (51) is arranged in one end of the opening. The patient optical fiber may be inserted in the other end of the opening so that the proximal end of the patient optical fiber is arranged in register with the distal end of the connection optical fiber in order to transmit light between the optical fibers. A spring (73) is arranged in the connector for exerting a force at the patient optical fiber at a side surface thereof for preventing unintentional withdrawal of the patient optical fiber. However, when the withdrawal force is larger than the removal force of the patch, the patient optical fiber is withdrawn from the connector. Thus, the patch is not removed from the skin even when a large force is exerted on the optical fibers.
